This invention relates to a process for transforming cells and is in the field of recombinant DNA technology.
The hereditary properties of a cell can be artificially changed by means of recombinant DNA techniques by integrating foreign DNA into the DNA of this cell. This DNA may originate from other cells which need not have a connection with the organism to be transformed.
The object of this genetic manipulation is often to transmit genetic properties from cells having a specific desired hereditary property to cells not having this property. For instance, there is the transmission of resistance to a specific toxic product, e.g., a herbicide, from a resistant plant-species to a nonresistant variant of the same species or to a nonresistant other species within the same family or even to a nonresistant species of another, more or less related family. There is also the transmission of the ability of producing a substance useful for medicaments or other purposes, e.g., from plants producing that substance to plants growing in other climates and lacking the ability of producing the substance. Furthermore, there is the transformation of animal and even human cell lines so as to use them for the production of a desired substance. Genetic manipulation is often connected with great problems, e.g., owing to the dissimilarity of the structure and organization of the donor and receptor cell, and in particular the genome thereof.
In the methods hitherto described for transforming cells by means of recombinant DNA techniques the following procedure is generally adopted. A gene (or group of genes) coding for a specific desired property or a specific product is identified and isolated from a suitable donor cell. This gene is often obtained through copy DNA (cDNA) of the messenger RNA transcribed therefrom (mRNA). This DNA is then cloned in a vector which may be multiplied in a suitable microorganism. A great problem is often how to obtain a clone containing a complete copy of the desired gene. If this has proved to be a success, the gene is often to be provided with suitable regulatory elements for use in the receptor cell which may sometimes be strongly different from the regulatory elements of the donor cell. Finally, the gene including the regulatory elements is transmitted to the receptor cell by means of so-called shuttle vectors or by means of direct transformation methods.
These known processes for transforming cells have a number of drawbacks. In the first place, the isolation and characterization of the gene to be transmitted require a good deal of expensive research that has to be financed before one has a single transformant in hands. The nature of the research further involves that highly specialized laboratory facilities and highly qualified staff members are required such as they are available only in few places in the world.
Secondly, a very thorough examination of the regulatory elements and signals applicable in the receptor is required. Thirdly, it is necessary to construct vectors and shuttle vectors adapted to donor and receptor. For many receptor organisms suitable shuttle vectors have not yet been found or developed.
Consequently, there is a need for a process for transforming cells which does not show the above drawbacks.